title: The use of solar radiation by the photosynthetic bacterium, Rhodopseudomonas palustris: model simulation of conditions found in a shallow pond or a flatbed reactor.
abstract: Photosynthetic bacteria are attractive for biotechnology because they produce no oxygen and so H2 -production is not inhibited by oxygen as occurs in oxygenic photoorganisms. Rhodopseudomonas palustris and Afifella marina containing BChl a can use irradiances from violet near-UV (VNUV) to orange (350-650 nm) light and near-infrared (NIR) light (762-870 nm). Blue diode-based pulse amplitude modulation technology was used to measure their photosynthetic electron transport rate (ETR). ETR vs Irradiance curves fitted the waiting-in-line model--ETR = (ETRmax × E/Eopt) × exp (1 - E/Eopt). The equation was integrated over pond depth to calculate ETR of Afifella and Rhodopseudomonas in a pond up to 30 cm deep (A376, 1 cm = 0.1). Afifella saturates at low irradiances and so photoinhibition results in very low photosynthesis in a pond. Rhodopseudomonas saturates at ≈15% sunlight and shows photoinhibition in the surface layers of the pond. Total ETR is ≈335 μmol (e(-)) m(-2) s(-1) in NUV + photosynthetically active radiation light (350-700 nm). Daily ETR curves saturate at low irradiances and have a square-wave shape: ≈11-13 mol (e(-)) m(-2) day(-1) (350-700 nm). Up to 20-24% of daily 350-700 nm irradiance can be converted into ETR. NIR is absorbed by water and so competes with the bacterial RC-2 photosystem for photons.
authors.affiliation: Tropical Plant Biology Unit, Faculty of Technology and Environment, Prince of Songkla University-Phuket, Kathu, Thailand.
authors.forename: Raymond J
authors.initials: RJ
authors.lastname: Ritchie
mesh_terms: D001429:Bacteriochlorophylls / Q000378:metabolism; D019149:Bioreactors; D008954:Models, Biological; D010788:Photosynthesis; D061005:Ponds; D012241:Rhodopseudomonas / Q000378:metabolism / Q000502:physiology*; D013472:Sunlight
chemical_list: D001429:Bacteriochlorophylls